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A primary difference between ammonites and ... is the variation in the shape and size of the shell ... required a larger body size for egg production. ...
A cross-section of a Nautilus pompilius shell, showing the large body chamber, shrinking camerae, concave septa, and septal necks (partial siphuncle supports) All nautiloids have a large external shell, divided into a narrowing chambered region (the phragmocone) and a broad, open body chamber occupied by the animal in life. The outer wall of ...
Goniatite shells are small to medium in size, almost always less than 15 centimeters (5.9 inches) in diameter and often smaller than 5 centimeters (2.0 inches) in diameter. The shell is always planispirally coiled, unlike those of Mesozoic ammonites in which some are trochoidal and even aberrant (called heteromorphs).
The main difference is that the Rutoceratidae are included with the Aipocerataceae of Kummel (1964) in the Rutoceratina. The remaining Tainocerataceae are the Tainoceratina. Rousseau Flower (1950) distinguished the Solenochilida, Rutoceratida, and Centroceratida, as separate orders, from the Nautilida, derived from the Barrandeocerida, which ...
Morphology of a male skeleton shrimp, Caprella mutica Morphology in biology is the study of the form and structure of organisms and their specific structural features. [1]This includes aspects of the outward appearance (shape, structure, color, pattern, size), i.e. external morphology (or eidonomy), as well as the form and structure of internal parts like bones and organs, i.e. internal ...
Modern groups of animals can be grouped by the arrangement of their body structures, so are said to possess different body plans. A body plan, Bauplan (pl. German: Baupläne), or ground plan is a set of morphological features common to many members of a phylum of animals. [1] The vertebrates share one body plan, while invertebrates have many.
Internal features can also show symmetry, for example the tubes in the human body (responsible for transporting gases, nutrients, and waste products) which are cylindrical and have several planes of symmetry. Biological symmetry can be thought of as a balanced distribution of duplicate body parts or shapes within the body of an organism.
Most of the generic names in this list come from Jack Sepkoski's 2002 compendium of marine fossil genera, which can be corroborated by other sources such as Part L, Ammonoidea, in the Treatise on Invertebrate Paleontology. Additional generic names included come from the Treatise or various peer review scientific journals.